Capacitive transient detector of high sensitivity

Abstract
A capacitive detector is described which displays high sensitivity and accuracy in the measurement of transients. The device has been used in an LC circuit for studies of third sound in thin helium films. When operated in a phase‐lock mode at 21 MHz its observed sensitivity is 15 Hz per angstrom of helium film thickness; changes in average film thickness as small as 0.01 Å have been detected